Polyolefins, as a class of materials, tend to have excellent physical and chemical properties and are useful materials for fibers, films, and other molding resins. Improvement of polymer properties is a dominant factor in the development and production of olefin polymers. Several methods have been employed to improve various polymer properties. Prior art teaches that reinforcing agents, such as glass, can be incorporated into the polymer to improve mechanical properties or to improve heat resistance. However, satisfactory improvements in the mechanical properties and/or heat resistance cannot be obtained by simply mixing glass fibers in a polyolefin because the bonding strength between the glass fibers and polyolefin is weak. Thus, such polymers must have a more "bondable" component grafted thereon to facilitate reinforcement with glass fibers and other generally infusible reinforcing agents.
Polymers with relatively high melting points, such as, for example, stereoregular polymers of branched, higher alpha-olefins, have been developed. These polymers are useful in high temperature applications, such as, for example, microwave packaging. Improving the thermal performance and/or properties of these polymers could expand the uses of these polymers, for example, as electrical and/or electronic connectors, automobile parts, and electric appliances. Because of the relatively high melting points and even higher melt processing temperatures, these polymers are thermally unstable and can be very susceptible to thermal degradation. Therefore, it is difficult to graft, and optionally reinforce, stereoregular polymers of branched, higher alpha-olefins in a melt process, such as can be done with other polyolefins such as polyethylene or polypropylene.
Grafting, or chemically modifying, polyolefins, especially relatively low melting point polymers, such as polyethylene and polypropylene, can be done alone or in combination with the addition of a reinforcing agent. Prior art teaches many grafting compounds, as well as several grafting processes. Grafting usually is done in the presence of a free radical generator and usually by a solution or melt process. Unfortunately, the presence of a free radical generator is also known to cause degradation of the polymer. Furthermore, a melt grafting process is also known to be detrimental to the properties of stereoregular polymers of branched, higher alpha-olefins. Prior art teaches that stereoregular polymers of branched, higher alpha-olefins, preferably, are grafted by a solution process.
Polyolefins are vulnerable to thermal-oxidative degradation due to exposure to heat or oxygen during processing and/or storage. To preserve desirable polymer properties, an antioxidant or stabilizer is sometimes used to inhibit discoloration and/or molecular deterioration. An unstabilized polyolefin can be susceptible to rapid deterioration over time. Unfortunately, the use of a stabilizer can have a detrimental effect on the grafting process. Stabilizers function as radical scavengers and peroxide decomposers. Stabilizers can hinder, if not halt, the grafting reaction.